Yes the motherboard supports DDR2 800. The memory is much faster than the CPU needs. Good for overclocking. You only need DDR2 533 for default settings.
Check the Asus site for qualified vendor list for memory to make sure it is recommmended for the board.
Also note that a lot of the issues have to do with the fact that much/most higher-end DDR2 RAM is sold according to speed/latency measured under non-standard conditions (e.g. higher DIMM voltage than the 1.8V DDR2 standard). This post may help clarify things: http://forumz.tomshardware.com/hardware/modules.php?nam...
Unfortunately, some memory manufacturers have focused so much on these non-standard conditions that their modules sometimes won't work at all under standard conditions! Hence, the reports of problems/incompatibility.